InP quantum dots in (1 0 0) GaP: Growth and luminescence

We describe the growth and optical emission from strained InP quantum wells and quantum dots grown on GaP substrates using gas-source molecular beam epitaxy. Self-organized quantum dot formation takes place for InP coverage greater than 1.8 monolayers on the (1 0 0) GaP surface. Atomic force and scanning-electron microscopy studies indicate that unburied dots have a lateral size of 60–100 nm and are about 20 nm high, with dot densities in the range of 2–6×10⁸ cm⁻² for InP coverage between 1.9 and 5.8 MLs. Intense photoluminescence is emitted from both the quantum wells and the quantum dots at energies of about 2.2 and 2.0 eV, respectively. Time-resolved measurements indicate rather long carrier lifetimes of about 19 ns in the quantum wells and about 3 ns in the quantum dots. The data indicate that the InP/GaP quantum wells form a type-II band system, with electrons in the X valleys of the GaP recombine with holes in the InP. Furthermore, in the InP/GaP quantum dot system, the conduction band edge in the X valley of the GaP is nearly aligned with that in the Γ valley of the InP. Rapid thermal annealing of the quantum dots results in at least a six-fold enhancement of integrated emission intensity as well as some Ga-In interdiffusion. The low interdiffusion activation energy indicates that the material near the interface between the GaP matrix and the InP dots is not free of defects.     

KDB: a fast update and high speed packet classifier in SDN

The Journal of Supercomputing - Packet classification is a fundamental function to support several services of software defined networking (SDN). Increasing complexity of the flow tables in SDN...     

An improved bat optimization algorithm to solve the tasks scheduling problem in open shop

Neural Computing and Applications - The open shop scheduling problem involves a set of activities that should be run on a limited set of machines. The purpose of scheduling open shops problem is to...     

The influences of collector diameter,spinneret rotational speed,voltage, and polymer concentration on the degree of nanofibers alignment generated by electrocentrifugal spinning method : Modeling and optimization by response surface methodology

We studied the capability of electrocentrifuge-spinning (ECS) method for generating highly aligned nanofiber. First, the degree of nanofiber alignment (DNA) produced by ECS was compared with that of rotating drum (RD) method and ECS superiority was demonstrated. Then central composite design (CCD) and response surface methodology (RSM) was used for optimization of operating conditions. The critical factors selected for the examination were voltage, polymer concentration, collector diameter and spinneret rotational speed. To design the required experiments at the settings of independent parameters, RSM was applied. A total of 30 experiments were accomplished towards the construction of a quadratic model for target variable. Using this quadratic model, the influence of aforementioned variables was discussed on DNA. The best operating condition for attaining the maximum value of DNA was the applied voltage of 20.19 kV, polymer concentration of 17.44wt%, collector diameter of 40.76 cm, and rotational speed of 2680.10 rpm.     

Two‐phase natural convection analysis and hybrid nanoparticle migration around micromixer blades

In this paper, numerical investigations are presented for hybrid nanoparticle migration and free convection heat transfer of two kinds of nanofluids in a micromixer at the fixed propeller condition. The inner blades and outer crust of the micromixer are kept at constant hot and cold temperatures, respectively. Two kinds of hybrid nanofluids, TiO₂‐CuO water and ethylene glycol‐(MoS₂‐SiO₂), are considered. The governing equations including velocity, pressure, temperature formulation, and nanoparticle concentrations are solved by a partial differential equation solver based on the Galerkin finite element method. The results are discussed based on the governing parameters, such as nanoparticle volume fraction, thermal and solutal Rayleigh numbers. The average Nusselt number was found to increase with the increasing nanoparticle volume fractions. Also, increasing the thermal Rayleigh number enhanced heat transfer while the solutal Rayleigh number has an insignificant effect on it. More importantly, increasing the thermal Rayleigh number assisted avoiding the agglomeration of nanoparticles around the blades and ensured more uniform nanoparticle distribution.     

PRSV equation of state parameter modeling through artificial neural network and adaptive network-based fuzzy inference system

Two different modeling methods have been proposed to relate the Peng-Robinson-Stryjek-Vera (PRSV) parameter, κ ₁, to some common thermodynamic constants, including critical temperature (T _c ), critical pressure (P _c ), acentric factor (ω) and molecular weight (Mw). The methods are artificial neural network (ANN) and adaptive networkbased fuzzy inference System (ANFIS). A set of 159 data points (116, 23 and 20) was used for construct training, validating and testing, respectively. The radius parameter of ANFIS was determined through genetic algorithm (GA) optimization technique. The ANN and especially ANFIS results are in a good agreement with most of the compound groups.     

Optimization of supercritical extraction of nimbin from neem seeds in presence of methanol as co-solvent

Mathematical modeling and optimization of the extraction of nimbin from neem seeds using supercritical carbon dioxide with methanol as co-solvent is the subject of this study. At first a correlation for Sherwood number (Sh) as a function of Reynolds number (Re) and Schmidt number (Sc) was proposed using a Genetic Algorithm (GA) technique. This correlation was compared to previous correlations and was found to give the most accurate results. Moreover, optimum conditions (temperature, pressure, solvent flow rate and particle diameter) which maximizes the extraction yield have been determined using GA. At the next step, methanol was used as a co-solvent and the dynamic equilibrium constant of solute between the solid phase and the solvent was estimated. By applying the new determined equilibrium constant, good agreement between the model and experimental data was observed.     

UPLC and HPLC of caffeoyl esters in wild and cultivated Arctium lappa L.

Analytical methods including ultra-performance liquid chromatography (UPLC) and high-performance liquid chromatography (HPLC) with photodiode array (PDA) detector were developed for the analysis of caffeoylquinic acid derivatives in seeds, leaves and roots of Arctium lappa L. Separation was performed on C₁₈ column utilising 5% (v/v) acetic acid in water and acetonitrile at 330 nm. Both methodologies were validated in terms of linearity, precision, and recovery. The results showed that the major advantages of UPLC, over HPLC were the fast analysis, narrow peaks, high sensitivity, and reduction of solvent consumption. Subsequently the methods were applied for the identification and quantification of chlorogenic acid (5-CQA) and 1,5-dicaffeoylquinic acid (1,5-DCQA) as main compounds in samples. The total phenolic content of samples ranged from 3.93 to 14.13 g of 5-CQA equivalent/100 g dry weight (DW). There was a significant variability from 89 to 571 mg/100 g for 5-CQA and 48 to 486 mg/100 g for 1,5-DCQA in dry material.     

Comparison of the effect of laminar and turbulent flow regimes on thermal stresses and strains in an annular fin

Journal of Mechanical Science and Technology - We compared the effect of laminar and turbulent flow regimes on thermal stresses and strains in an annular fin. This comparison showed that...     

Production and evaluation of the surface properties of chiral poly(amide-imide)/TiO2 nanocomposites containing L-phenylalanine units

This study concerted on the immobilization of nano-titanium dioxide particles (TiO₂, 30–50 nm particle size) into or onto an optically active poly(amide-imide) (PAI). The matrix PAI consisted of the chiral units in the main and hydroxybenzamide functional groups in the side chains. The macromolecule structure has been fabricated from the reaction of 3,5-diamino-N-(4-hydroxyphenyl) benzamide and N,N′-(pyromellitoyl)-bis-L-phenylalanine diacid chloride at low temperature. The hydroxyl groups on the side chains of the PAI could provide better compatibility and bonding, which cause to suitable homogenous dispersion of nanoparticles (NPs) in the obtained nanocomposites (NCs). Also due to prevention of aggregation, the surface of TiO₂ NPs was functionalized by 3-aminopropyltri-ethoxysilane as a coupling agent to introduce amine groups on the NPs surfaces. Atomic force microscopy, field emission scanning electron microscopy, transmission electron microscopy and contact angle measurements were used for investigation of the surface properties of obtained NCs. These results confirmed the well-dispersion of nanoTiO₂ in the PAI matrix.